A method for preparing infrared test samples of low glass transition temperature aqueous polymer emulsions

Abstract

The invention provides a sample preparation technology for infrared spectroscopy analysis test of low glass transition temperature aqueous polymer emulsion, which belongs to the field of infrared spectroscopy analysis sample preparation. The invention aims to solve the problem that the sample of low glass transition temperature (Tg) aqueous polymer emulsion presents a continuous viscous state or viscoelastic state under the conditions of drying to remove water or freeze drying to remove water, and cannot be ground or dispersed into powder, and thus cannot be prepared by potassium bromide tableting method. First, the polymer emulsion is diluted with deionized water, demulsified with potassium bromide, and then fully freeze-dried at low temperature to remove water, and a small amount of powder sample is taken for grinding and tableting to obtain an infrared test sample. Selecting potassium bromide for demulsification avoids the interference peaks caused by other impurities during the test process.

Description

Technical Field

[0001] The invention discloses an infrared test sample preparation method applicable to an aqueous polymer emulsion with a low glass transition temperature, and belongs to the field of infrared spectrum analysis sample preparation. Background Art

[0002] Infrared spectroscopy is a common analytical method for qualitative analysis of the molecules of a substance. In the infrared spectroscopy test method, predecessors have mentioned a variety of sample preparation methods, which are divided into: 1. Solid samples; 2. Liquid samples; 3. Gas samples; 4. Reflection method to prepare samples. The most commonly used sample types are solid samples and liquid samples. Among them, the solid sample preparation method is divided into: ① Infusible and insoluble samples, potassium bromide powder is often used for solid tableting, which can be convenient and effective for infrared spectroscopy testing. ② Thin film samples, through the solution film and hot pressing film method, the defect is that the film is not easy to be completely removed, and the sample preparation speed is slow. ③ Powder samples, using halide tableting and paraffin paste method. ④ Fiber samples, potassium bromide tableting method can be used, the fiber needs to be cut into fine powder, cold pressing tableting method needs to cut the fiber into a few millimeters long, through a metal mesh screen on the potassium bromide salt sheet, and then oil pressure molding. In addition, there are other special sample preparation methods such as straightening method and hot melt method. Liquid sample preparation method: If the sample is not volatile, the liquid film method is used. The liquid is dropped on a potassium bromide salt sheet, clamped with another potassium bromide salt sheet and placed in the sample chamber for measurement. If the sample is volatile, the solution method is used. However, since there is a certain amount of water in the emulsion sample, water interference will occur during the test process. Usually, heating drying or freeze drying is used to remove the water. If the glass transition temperature of the emulsion is low, it will present a continuous viscous state or viscoelastic state after drying to remove the water; the same is true after freeze drying. The sample has a large viscoelasticity and cannot be tested using the solid sample test method. Summary of the invention

[0003] In view of the deficiencies of the prior art, the object of the present invention is to provide a method for preparing samples in infrared spectroscopy analysis test of aqueous polymer emulsions with low glass transition temperature.

[0004] In order to achieve the above purpose, the technical scheme of the present invention is as follows: take a small amount of emulsion, dilute it with deionized water, take the diluted sample and place it in a culture dish, add a large amount of potassium bromide to break the emulsion, perform sufficient vacuum freeze drying, and after the freeze drying is completed, take a small amount of sample for tableting and infrared spectroscopy analysis.

[0005] The specific steps include:

[0006] (1) Take a 0.3-0.5 ml sample of the emulsion to be tested and dilute the emulsion 40-60 times with deionized water;

[0007] (2) Sample the diluted solution and place it in a clean culture dish. The amount used is 1.5 to 2 g.

[0008] (3) Weigh 3-5 g of solid potassium bromide powder and add it to the diluent in the culture dish. Stir well and seal with plastic wrap to prevent sample contamination.

[0009] (4) Place the culture dish in a refrigerator at -(15-20)°C for 12 to 24 hours;

[0010] (5) Take out the culture dish, poke several small holes in the plastic wrap at the sealing part, and put it into a vacuum freeze dryer at -50°C for vacuum freeze drying for 48 to 72 hours;

[0011] (6) Grinding an appropriate amount of potassium bromide, pressing into tablets, and performing a potassium bromide background test of infrared spectroscopy;

[0012] (7) Take out the dried sample, take an appropriate amount of the sample and potassium bromide, put them into an agate mortar and grind them thoroughly, and use a mold to press them into tablets to obtain the sample to be tested;

[0013] (8) Conduct infrared spectrum test on the sample to be tested.

[0014] Further, in step (1), 0.4 ml of the emulsion to be tested is sampled and the emulsion is diluted 50 times with deionized water;

[0015] Furthermore, the amount of the diluent used in step (2) is 2 g;

[0016] Further, in step (3), 3 g of solid potassium bromide powder was weighed;

[0017] Furthermore, in step (4), the culture dish is placed in a refrigerator and frozen at -20°C for 24 hours;

[0018] Furthermore, step (5) is freeze-dried in vacuum for 48 hours.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In order to solve the problem that the aqueous polymer emulsion with low glass transition temperature (Tg) presents a continuous viscous state or a viscoelastic state under the conditions of drying to remove water or freeze drying to remove water, and cannot be ground and dispersed into powder, and thus cannot be prepared by potassium bromide tableting method, the present invention first dilutes the polymer emulsion with deionized water, uses potassium bromide to break the emulsion, and then fully freeze-dries at low temperature to remove water, takes a small amount of powder sample for grinding and tableting, and prepares an infrared test sample. Selecting potassium bromide for demulsification avoids the interference peaks caused by other impurities in the test process. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific implementation modes.

[0022] Example 1: A method for preparing infrared test samples of low Tg value aqueous polymer emulsions, wherein potassium bromide is added after diluting the emulsion sample, and the sample is taken out after freezing pretreatment in a refrigerator, freeze-dried in a vacuum environment, ground and pressed into tablets to obtain the sample to be tested. The low Tg value range of the aqueous polymer emulsion is -80 to 20°C, the amount of the emulsion taken is 0.3 to 0.5 ml, the dilution multiple selected for the emulsion dilution is 40 to 60 times, the amount of the diluent taken is 1.5 to 2 g, the amount of potassium bromide added is 3 to 5 g, the freeze-drying temperature is -50°C, the sample is frozen in the refrigerator for 12 to 24 hours, the vacuum freeze-drying time is 48 to 72 hours, and the environment in the freeze-drying box is a vacuum environment.

[0023] Embodiment 2:

[0024] Select 0.4ml of emulsion and dilute it to 50 times with deionized water, take 2g of the diluted sample and place it in a clean culture dish, add 3g of potassium bromide, stir and mix thoroughly, and seal the culture dish with a clean plastic wrap; put the sample in a -20℃ environment for freezing pretreatment for 24 hours; take out the sample, poke several small holes in the sealing plastic wrap, and fully freeze-dry it in a freeze dryer at a vacuum environment of -50℃ for 48 hours. Use pure potassium bromide to grind and press the tablet to test the potassium bromide background. Take out the freeze-dried sample and press it into a tablet as soon as possible. When pressing the tablet, the salt tablets used to test the potassium bromide background can be directly placed in an agate mortar for full grinding. After the tablet is pressed, perform infrared spectrum test.

[0025] In summary: The present invention discloses a sample preparation technology for infrared spectroscopy analysis test of a low glass transition temperature aqueous polymer emulsion, which belongs to the field of infrared spectroscopy analysis sample preparation. It is designed to solve the problem that the sample of the low glass transition temperature (Tg) aqueous polymer emulsion is in a continuous viscous state or viscoelastic state under the conditions of drying to remove moisture or freeze drying to remove moisture, and cannot be ground or dispersed into powder, and thus cannot be prepared using the potassium bromide tableting method. First, the polymer emulsion is diluted with deionized water, demulsified with potassium bromide, and then fully freeze-dried at low temperature to remove moisture, and a small amount of powder sample is taken for grinding and tableting to obtain an infrared test sample. Selecting potassium bromide for demulsification avoids the interference peaks caused by other impurities during the test process.

Claims

1. A method for preparing infrared test samples of low glass transition temperature aqueous polymer emulsions, characterized in that: The emulsion sample is diluted and potassium bromide is added, and the sample is taken out after freezing pretreatment in a refrigerator, freeze-dried under a vacuum environment, and ground and pressed into tablets to obtain a sample to be tested; the specific steps include: (1) Take a 0.3-0.5 ml sample of the emulsion to be tested and dilute the emulsion 40-60 times with deionized water; (2) Sample the diluted solution and place it in a clean culture dish. The amount used is 1.5 to 2 g. (3) Weigh 3-5 g of solid potassium bromide powder and add it to the diluent in the culture dish. Stir well and seal with plastic wrap to prevent sample contamination. (4) Place the culture dish in a refrigerator at -(15-20)°C for 12 to 24 hours; (5) Take out the culture dish, poke several small holes in the plastic wrap at the sealing part, and put it into a vacuum freeze dryer at -50°C for vacuum freeze drying for 48 to 72 hours; (6) Grinding an appropriate amount of potassium bromide, pressing into tablets, and performing a potassium bromide background test of infrared spectroscopy; (7) Take out the dried sample, take an appropriate amount of the sample and potassium bromide, put them into an agate mortar and grind them thoroughly, and use a mold to press them into tablets to obtain the sample to be tested; (8) Conduct infrared spectrum test on the sample to be tested.

2. The method for preparing infrared test samples of a low glass transition temperature aqueous polymer emulsion according to claim 1, characterized in that: In step (1), 0.4 ml of the emulsion to be tested is sampled and the emulsion is diluted 50 times with deionized water.

3. The method for preparing infrared test samples of a low glass transition temperature aqueous polymer emulsion according to claim 1, characterized in that: The amount of the diluent used in step (2) is 2 g.

4. The method for preparing infrared test samples of a low glass transition temperature aqueous polymer emulsion according to claim 1, characterized in that: In step (3), 3 g of solid potassium bromide powder was weighed.

5. The method for preparing infrared test samples of a low glass transition temperature aqueous polymer emulsion according to claim 1, characterized in that: In step (4), the culture dish is placed in a refrigerator and frozen at -20°C for 24 hours.

6. The method for preparing infrared test samples of a low glass transition temperature aqueous polymer emulsion according to claim 1, characterized in that: Step (5) vacuum freeze drying for 48 hours.